Properties of New Low Dielectric Constant Spin-on Silicon Oxide based Polymers

Conclusions

The properties of three types of Si-O polymers have been described. The newer methylsilsesquioxanes and inorganic polymers have low dielectric constant because the silanol has been eliminated form the cured film. Both types of low k materials, after cure, are stable in a room temperature ambient. The low k values, stress and refractive index remain constant with time. However there are thermal limitations for maintaining these properties. The inorganic polymer starts to degrade at temperatures above 425 °C while the methylsilsequioxane is stable at 550 °C under vacuum.

The major issue for all new low k materials is process integration. While these new polymers are designed with silicon and oxygen in the backbone to have properties that are similar to SI0 2, the processing use for etching and removal of photoresist needs to be modified to accommodate the fact that they are not identical to Si0₂ (k = 4.0).